Electrostatic interaction-enhanced chromophore reaction: a cationic pyridinium-functionalized pyrrolopyrrole aza-BODIPY fluorophore for highly efficient H2S detection†

Fluorescence detection of hydrogen sulfide (H₂S) has received more attention owing to its vital role in food safety and environmental pollution. Currently, most existing probes show sluggish reactivity, minor spectral changes and strong interference. In this work, we developed a cationic pyridinium-functionalized pyrrolopyrrole aza-BODIPY fluorescent probe (PPAB-Ps) for highly efficient H₂S sensing through electrostatic interaction-enhanced chromophore reaction. PPAB-Ps exhibited naked-eye discernible color and fluorescence changes (Δλ_abs = 165 nm and Δλ_em = 179 nm), fast response (∼2 min), good selectivity, and a low limit of detection (88.4 nM). In addition to H₂S-containing aqueous solution, H₂S vapor generated distinct dual-signal changes. The practical applications included good recovery of H₂S in real water and beer samples. More importantly, a strong correlation was found between the color change of PPAB-Ps-loaded test paper, induced by meat spoilage, and total volatile basic nitrogen (TVB-N) content. Visual monitoring of shrimp and pork freshness was achieved through a smartphone-adaptable color app. This work provides a novel sensing strategy for improving H₂S detection performance and offers a promising platform for the rapid and convenient evaluation of H₂S in food samples in a non-destructive manner.